This
website deals with the Yellow-legged Gull taxon michahellis, which
is a common migrant from July to December in NW Europe. After extensive expansion
of the breeding population during the last three decades, it nowadays can
be found breeding in Belgium, the Netherlands and Britain in mixed couples
with both Herring Gull (argenteus) and Lesser Black-backed Gull (graellsii).
There are subtle differences between the populations from the
Mediterranean, Atlantic coast of Portugal and Morocco and from the islands
in the Atlantic. Most pronounced differences can be found in the taxon atlantis,
now regarded as full species by some authors and birds along the Atlantic coast of the Iberian peninsular: lusitanius. Both atlantis and lusitanius are treated in their own sections on this website.

General
description:

Identification
of juvenile Yellow-legged Gulls isn't always easy, but with a
combination of characteristics, positive identification must be possible in
almost all of them. Within the region (NW Europe), most confusion
may arise with juvenile Herring Gulls argentatus and argenteus and juvenile Lesser Black-backed Gulls graellsii. Juvenile white-headed gulls from E and SE Europe,
e.g. Steppe Gull cachinnans, Baraba Gullbarabensis, andArmenian
Gullarmenicus are other candidates for causing problems, and some of the birds may be best left unidetified.

Yellow-legged
Gullmichahellis 1CY, July 25 2010, Rosas, Cataluna, Spain. Picture: Chris Gibbins. Close to "the average michahellis": typical upperwing pattern, with only weak paler innerwebs on inner primaries and no pale lozenges on the outerwebs. Most of GC with dark centres. Tail with wedge-shaped band and limited proximal spotting on rectrices is common in Med. michahellis. Overall reddish brown plumage.

Rather
dark inner primaries compared to argenteus and cachinnans,
the window is rather ill-defined (see image
5545), but the inner primaries are not all dark as in
most graellsii;

Normally
the tertials show an all dark tertial-centre with a smooth white
fringe as in graellsii (see image
5699). The tertials are normally not as obviously
notched as in argenteus.Michahellis may show a
broad well-defined pale bar between the sub-terminal band and
the dark centre (a transversal bar), but some variations of the
pattern occurs (see also image 5707);

Pale
under-parts: normally a streaked breast-band contrasts with the
white chin and the pale belly (see image
5698). The under-parts in argenteus are overall
warm coloured, more yellow-brown. In fresh juvenile graellsii the brown sides of the neck are often connected to the brown
ear-coverts and the brown runs from the crown to the breast,
forming a larger all brown patch;

Greater
coverts often lack the 'piano' pattern in michahellis; a
pattern obvious in argenteus (see image
5699). The outermost greater coverts become gradually
darker, with only a thin white fringe running all the way to the
base. Nevertheless, in some michahellis the greater
covert pattern may resemble that of argenteus. Juvenile cachinnans in July normally still show a fresh broad creamy-white tip to
the median coverts, creating what might be called a pale bar at
the folded wing, when observed from a distance. Michahellis normally lacks this bar and by July, the median coverts may
appear slightly worn at the tips already, especially the
innermost medians;

Under-wings
are dark clouded or with a vermiculate pattern, much darker than
the average cachinnans;

Shins
are often pale, not contrasting with the rest of the legs (see image
5578); the shins are often dark in graellsii;

The
tail-band is broadest at the centre, becoming smaller at outer
tail feathers, so obviously different from the broad dark
tail-band commonly seen in graellsii and argenteus (see image 11);

The
upper-parts are not rich yellow-coloured as in argenteus,
but rather cold pale brown (see e.g. image
5545), with white fringes and brown centres to the
scapulars and coverts. Contrary cachinnans, michahellis normally lacks the neat post stamp fringes in the lower
scapulars which may be very obvious in cachinnans. By
July, michahellis actively moult upper and upper lower
scapulars and the juvenile lower scapulars have abraded fringes
(for terms used: see Topography
section);

Moult
in the upper-parts starts early in the season in michahellis,
as can be seen in many images. Michahellis has early
fledglings, consequently has more untidy looking plumage in
mid-summer juveniles.

Juvenile michahellis by the end of July

One
of the most striking characteristics of 1CY michahellis is it's quick moult. As early as the end of July, many scapulars,
mantle feathers and sometimes tertials or wing-coverts are
shed or replaced by post-juvenile feathers. From 26 to
30 July 2001, we described 59 juvenile michahellis at NW
France: at Etaples (Le Tourquet) and at Le Portel (Boulogne-sur-Mer:
50.42 N, 1.34 E). All present juveniles were included. Over the period, we may have described (incidentally) the
same bird when we visited fixed locations (but we kept those
counts separated), and the general conclusions on bird present at
this location presented here will
stand, supported by the images shown at this page.

The
general idea is that michahellis, after leaving the colonies
in June or July, quickly starts the post-juvenile moult. The first
signs of moult are usually detected in the upper scapulars and
mantlefeathers, followed by other parts of the body-feathers and
sometimes upperwingcoverts and/or tertials.

The
retained juvenile feathers are normally very fresh or only very
slightly abraded. Given this good quality of the feathers during
this month, it is not likely that these feathers are replaced for
maintaining primary plumage functions (i.e. protective and
locomotoric) at the moment of renewal. It is likely that the
post-juvenile moult has been initiated in order to optimize primary
plumage functions during winter.

The
small survey in the period July 26-30 2001, showed only one single
bird
in complete juvenile plumage, i.e. not actively moulting scapulars
and mantle. The conclusion is that the vast majority (> 90%)
moult scapulars by the end of July and over 25% moult wing-coverts.
Only a few (< 5%) had shed tertials.

Juvenile michahellis moult score July 26-30 2001 Etaples &
Le Portel

(

50.42
N, 1.34 E )

new
mantle

new
scapulars

new
coverts

new
tertials

yes

no

yes

no

yes

no

yes

no

Etaples

25

0

22

3

4

21

0

25

n
= 25

Le
Portel

33

1

33

1

12

22

2

32

n
= 34

Notes:
Yes means: active moult started; bird shed at least one
feather of this tract, but some advanced birds may show
several 2nd generation feathers already.

Etaples count included some distant birds, making mantle score
more difficult. Le Portel counts were at close range.

Some birds were behind in moult, but nevertheless they could
show extensive wear, especially in the inner coverts, tertials
and lower rear scapulars.Scapular moult
often starts at the inner 2 median coverts. The next 2 or 3
are left juvenile, after which a few central feathers are
shed. In the greater coverts, the strategy may be similar, but
we only saw juveniles which had shed the innermost greater
coverts.
Only 2 juvenile michahellis were moulting tertials.

In
the same period a large gull resting place was visited near Venice,
Italy. Out of 51 juvenile michahellis, only 1 didn't start
moulting mantle feathers, 3 out of 51 didn't start moulting
scapulars. These figures are perfectly in line with the survey from
NW France. Regarding the moult in the coverts and tertials, birds in
Italy are slightly ahead of the birds in NW France.

Lignano,
Venice, Italy (45.28N-12.23E): July 27 and 29th 2001.
juvenile michahellis, n = 51. The results of this
survey are much in line with the observation made in NW
France.